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501 5.5.2 mailbox invalid for mailboxes that does exist

  • M

    Hi team,

     

    I've recently joined a client that uses MDeamon for their emails.... As I'm new to this, trying to get some experience and advices about fixing ongoing issues... 

     

    I have few users that from time to time are not able to send emails to their colleagues (so internal emails). Checking the logs, I see "501 5.5.2 mailbox invalid" for the failed recipients (sending email to several ppl where most of them are undeliverable and few from the list are delivered to with no issues). The mailboxes exist and other users can send to them with no issues.

     

    What could be causing this issue please? Been trying to go through "all" logs but nothing else then that "501.5.5.2" error give me any furhter info about how to tshoot.

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  • A

    Hi Michal,

    Can you post the entire SMTP session from the inbound SMTP log that shows the error occurring?  Please obfuscate any of the data that you would prefer to not share with the internet.  If you don't want to share any of the information with the internet, you can send it to me privately.  arron.caruth @ mdaemon.com.  Please reference this post.

    --
    Arron Caruth

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  • M

    Hi Arron,

     

    Thank you for reply. I have sent you the log via email.

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  • A

    What client is being used to send the email?

    Are the contacts being added to the To field from an address list or from auto complete information?

    It looks to me like the messages are being sent to the wrong addresses.

    Normally you will see this in the inbound SMTP log:

    Fri 2023-07-28 09:26:48.131: <-- RCPT TO: <user@domain.com>

    In the case when the messages are not accepted we are seeing this in the log:

    Fri 2023-07-28 09:26:48.131: <-- RCPT TO: <'user@domain.com'>

    Notice the single quotes around the email address.  They should not be there.

    I'm not sure why the contacts are being added incorrectly, but I'd start by checking the autocomplete information in the user's email client that was used to send the messages that failed to make sure the addresses are not saved incorrectly.  I'd also check all of the users contact lists to make sure they don't have contacts stored with incorrect formatting on the addresses.

    If you have a public contact list with all of the empoloyees, I'd also check it to make sure the addresses are correct.

    Basically, check anywhere the user might be using saved contact data from.

     

    --
    Arron Caruth

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  • M

    great catch with those quotes... didnt know about that ... yes it seems to be a wrong/typo in the receipient. What however confuses me is that I can see the exact same "receipient" used by other colleagues earlier and also later that day and it was delivered fine (no difference in the email address at all). I will ask the problematic user to type it manually and test it.... 

     

    Btw: users are using Outlook 2010

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